The invention relates to a display instrument, in particular for a vehicle, with a printed circuit board, at least one illuminable display area and at least one illuminating element, which has an LED and can be fastened on the printed circuit board by a contact socket.
Such display instruments are known and are used, for example, in motor vehicles in the form of so-called instrument clusters. These instruments are of a substantially modular construction, a central housing provided inter alia with light ducts for light guiding bearing on the rear side measuring elements and a printed circuit board and being provided with a closure cover. On the front side of the central housing, facing an observer, there is arranged an instrument panel with indicator needles and various display areas. To distinguish between them, the display areas are provided with various symbols and/or are differently colored. The latter serves at the same time for improving the signaling function of the display areas. A front frame with a cover glass forms the front termination of the instrument cluster.
On account of the modular construction of said instrument clusters, it is possible, depending on the customer""s requirements, to vary within broad limits both the instrumentation itself and its technical and visual design. It is obvious here to equip numerous different vehicle models with the same basic instrument and implement in it the desired additional functions according to requirements.
On account of the very great variety of models, however, it is necessary to keep in stock a large number of different printed circuit boards, which are fitted with the respectively required electronic circuits for activating the displays. Alternatively, one printed circuit board completely fitted with all the electronic circuits which may be required can be used, said printed circuit board being installed, irrespective of the detailed instrumentation, into each also only sparingly equippedxe2x80x94instrument.
Both specified possibilities lead to a very high expenditure in terms of production and logistics and make the display instruments expensive to a considerable extent.
To remedy this situation, it is the object of the present invention to provide a display instrument with an illuminable display area of the specified type in such a way that its production is simplified, its ease of servicing is increased and its service life is prolonged.
The object is achieved in the case of a display instrument of the specified type by the contact socket having a support component for activation electronics for activating the LED. In addition to achieving the object specified above, an instrument according to the invention offers greater functionality as well as simplified instrument construction and consequently increased assembly dependability.
It is in this case particularly favorable and further simplifies assembly and stockkeeping if the support component is connected to the contact socket and/or the LED, forming a single component.
However, it may be of advantagexe2x80x94for example when using standard componentsxe2x80x94if the support component is detachably connected to the contact socket and/or the LED. The connection used is, for example, a screw, plug-in or clip connection. If, on the other hand, it is not important that the individual components can be separated again, it is possible to connect the support component to the contact socket and/or the LED undetachably, for example by adhesive bonding, soldering, welding or inseparable locking.
In a particularly advantageous and compact embodiment of a display instrument according to the invention, the support component is a wall of the contact socket. In this case, it is particularly favorable if the support component is a side or end wall of the contact socket facing away from the printed circuit board. For example, a conceivable embodiment is one in which the support component is an end wall of the contact socket and electronic components of the activation electronics are arranged around an LED fitted on or in the end wall.
Conventional display instruments often have a considerable distance between an illuminating element, arranged on a printed circuit board, and a display area which can be illuminated by this illuminating element. To be able to illuminate the display area with adequate intensity over such a large distance, here it is only possible to use miniature incandescent lamps as the light source. If, in a preferred embodiment of a display instrument according to the invention, the illuminating element has an intermediate element which can be connected on one side to the contact socket and on an opposite side to the LED, then LEDs can be used as the light source, even in display instruments described above in which the printed circuit board and display area are at a not inconsiderable distance from each other. In comparison with miniature incandescent lamps, LEDs are much more reliable, they have a longer service life and are less sensitive to vibration. In particular in a case where a display instrument according to the invention is used in a vehicle, these advantages are of great significance.
Moreover, incandescent lamps have the disadvantage that they necessitate colored printing of the display areas or the use of color filters if a colored display is desired. LEDs on the other hand can themselves illuminate in color, for example red, yellow or green.
The intermediate element is preferably connected to the contact socket and/or the LED, forming a single component. This has the effect of simplifying assembly and also reducing storage expenditure in the production process.
It may be advantageous if the intermediate element is detachably connected to the contact socket and/or the LED. Conceivable here, for example, is a plug-in connection, which may be secured by clipping, or else a screw connection. In both cases, the flexibility with which the individual components can be used is increased. However, it may also be of advantage if the intermediate element is undetachably connected to the contact socket and/or the LED. Such a connection, which can be permanently maintained and is simple to produce, may be achieved, for example, by adhesive bonding, soldering, welding or locking, the latter only allowing destructive breaking up of the individual components.
In a particularly simple way, the intermediate element may be a tube, the wall of which may additionally be perforated, for example for reasons of heat dissipation or saving material. It is even more simple if the intermediate component is in bar form. It may in this case be a single bar, for example of rectangular or round cross section, or an arrangement of a plurality of corresponding bars.
Depending on the desired material properties and production possibilities, the intermediate element may advantageously consist of metal, plastic or a composite material. In a preferred embodiment, it is flexible and thus permits a largely unrestricted setting of the illuminating direction of the LED as well as simplified installation under confined spatial conditions.
It likewise simplifies assembly and logistics if the support component is connected to the intermediate element, forming a single component.
There are numerous possibilities for the connection of the contact socket to the printed circuit board. For instance, in a preferred embodiment of the invention, the contact socket is detachably connected to the printed circuit board. This connection may be, for example, a plug-in connection orxe2x80x94increasing the contact dependability and durability of the connection a plug-in/turning connection, for instance with a bayonet fastener. In an automated production process, it is similarly advantageous, however, if the contact socket is undetachably connected to the printed circuit board, for example by soldering.
It is known to fasten illuminating elements, having an LED, directly on a printed circuit board without using a contact socket (generally by soldering). In a display instrument, in particular for a vehicle, with a printed circuit board, at least one illuminable display area and at least one illuminating element which has an LED and can be fastened on the printed circuit board, the object described above is achieved by the illuminating element having a support component for activation electronics for activating the LED. Such an embodiment is particularly advantageous, since it is possible to dispense entirely with a contact socket as an additional component.
It is of particular advantage if the support component is a printed circuit board. It is particularly favorable, in particular for simple assembly as well as freedom of use under as many installation conditions as possible, if the printed circuit board is flexible.
To allow the support component to be both reliably identified and also installed in the correct position during the assembly operation, it advantageously has a coding, for example mechanical, optical or electronic, such as a recess or a color marking.
The support component preferably also has a spring element, which is, for example, fitted onto the support component and, if appropriate, may be additionally adhesively bonded or soldered to the latter. The spring element may, on the one hand, mechanically secure the support component on the printed circuit board, on which the illuminating element can be fastened, and, on the other hand, contact the activation electronics and the LED electrically with the aforementioned printed circuit board.
The support component could be inserted into a printed circuit board without an additional guard device. It is of particular advantage, however, if the support component has a housing guarding against dust and mechanical damage, which is, for example, screwed or fitted onto the support component. The housing preferably has in the region of one side facing away from the LED a recess or a lug and can in this way significantly simplify the handling of the support component. Easy identifiability of the color of the LED, without having to disassemble the LED from the printed circuit board, can be advantageously achieved if the housing has a color or partial coloration corresponding to the color of the LED.
The luminosity of the LED is fully utilized particularly well if the LED, the support component or the intermediate element has a reflector attachment.
In modern vehicles, on account of the extensive use of sensors for a wide variety of tasks, the significance and number of displays serving for monitoring have increased considerably. Here, the use of a color-changing LED in a display instrument according to the invention offers wide-ranging application possibilities. For example, if the activation electronics take the form of a color control for activating the LED, with such a color-changing LED a display of various operating states of a device can take place in a single symbol area. If this is used, for example, as an airbag control lamp, it is possible for example for a color-changing LED illuminating red to signal xe2x80x9cmalfunctionxe2x80x9d, whereas a yellow illumination of the same LED may mean xe2x80x9cswitched offxe2x80x9d.
If, according to another embodiment, the activation electronics take the form of a timing control for activating the LED, the latter may be used (in the case of a single-color LED) for illuminating a display area over a specific unit of time (for example eight seconds) after a specific operation (for example switching on the ignition). For example, the function of a seatbelt warning lamp would correspond to this.
Printed circuit boards are usually fitted with surface-mounted devices, which in particular simplify and speed up mass production. To allow the LED to be fitted by existing production installations and to achieve a short assembly time, the LED is therefore preferably a surface-mountable LED.
It is of particular advantage if the activation electronics have a resistor as a series resistor of the LED, in order to adapt the brightness of the LED to the light intensity of further display elements and the requirements of good perceptibility and non-glare display. The activation electronics preferably have a diode for decoupling the LED.